Metallic printing inks and metallized papers printed therewith

Abstract

A thermoplastic resin, a leafing grade aluminum paste, and a solvent are mixed to form a metallic printing ink which is useful for metallizing a wide range of paper stocks by selected conventional printing processes, such as rotogravure printing. The metallic ink can be applied at four pounds per ream (6.5 g/m 2 ) of dry coating to form a satisfactory moisture barrier, but the ink is similar to paint in that a glossy aluminum finish is produced by leafing of the aluminum particles when the coated paper is heated, as by passing the paper over a heated roll.

What is claimed is: 
     
       1. A metallic printing ink comprising a thermoplastic resin selected from the group consisting of substituted styrene copolymer resins, chlorinated rubber, and styrene resins; a leafing grade aluminum paste; and a solvent selected from the group consisting of toluene, methyl ethyl ketone, methyl isobutyl ketone, and mixtures thereof, said printing ink being applicable to coated papers and to uncoated papers and to plastics by printing processes to provide a brilliant finish after heat treatment at about 300° F.; and said ink being further characterized by being capable of drying to a non-tacky state when exposed to temperatures in the range of between about 150° and 200° F. for a period of from about 1 to about 3 seconds, and by said thermoplastic resin being sufficiently soft as to permit leafing of said leafing grade paste when said ink is applied as a printed coating on a paper base and said paper base is then passed over a roller heated to a temperature of between about 200° and about 400° F. for about 0.5 seconds of contact with said roller. 
     
     
       2. The metallic printing ink of claim 1 wherein one of said printing processes is rotogravure printing. 
     
     
       3. The metallic printing ink of claim 1 wherein said aluminum paste comprises about 62-72.5% by weight of aluminum flakes having a particle size distribution characterized by a retention of about up to 0.1% by weight on a 44-micron screen. 
     
     
       4. The metallic printing ink of claim 3 wherein said paste contains 1.0-3.0% by weight of stearic acid. 
     
     
       5. The metallic printing ink of claim 4 wherein said paste contains 24.5-37% by weight of exempt mineral spirits. 
     
     
       6. The metallic printing ink of claim 1 wherein said printing ink comprises by weight approximately: A. 42 weight percent of said resin binder;   B. 16 weight percent of said leafing grade aluminum paste; and   C. 42 weight percent of said solvent.   
     
     
       7. The metallic printing ink of claim 6 wherein said aluminum paste comprises by weight: A. 62-72.5 weight percent of finely divided aluminum flakes;   B. 1.0-3.0 weight percent of stearic acid; and   C. 24.5-37 weight percent of exempt mineral spirits.   
     
     
       8. A metallized paper consisting essentially of a paper base and a printed coating with the ink of claim 1, said printed coating having an infrared reflectance of 550 millimicrons wavelength light of at least 60 percent. 
     
     
       9. The metallized paper of claim 8 wherein said printed coating is applied directly onto said paper base by relief and intaglio printing processes. 
     
     
       10. The metallized paper of claim 9 wherein said paper base is natural kraft. 
     
     
       11. The metallized paper of claim 9 wherein said printed coating is appled at about 2.5 to 8 grams/square meter. 
     
     
       12. The metallized paper of claim 8 wherein said aluminum flakes have a particles size distribution characterized by a retention of up to about 0.1% by weight or a 44 micron screen. 
     
     
       13. The metallized paper of claim 12 wherein said printed coating is a moisture barrier. 
     
     
       14. The metallized paper of claim 13 wherein said printed coating is usable without a topcoat as holiday and gift wrapping papers, pouch papers, and as backing for fiberglass insulations, fiberboards, flakeboards, hardboards, and insulation boards. 
     
     
       15. A process for metallizing papers and plastics comprising: A. preparing a metallic printing ink which consists essentially of: (1) a thermoplastic resin binder selected from the group consisting of substituted styrene copolymer resins, chlorinated rubber, and styrene resins,   (2) a leafing grade aluminum paste, and   (3) a solvent selected from the group consisting of toluene, methyl ethyl ketone, methyl isobutyl ketone, and mixtures thereof;     B. applying said printing ink to a base selected from the group consisting of paper, paperboard, and plastic film by means of a printing process selected from the group consisting of relief and intaglio printing processes and drying said applied printing ink to form a metallized coating on said base; and   C. heat treating said coating at about 300° F. to cause said aluminum particles to come to the surface to form a highly reflecting coating.   
     
     
       16. The process of claim 15 wherein said aluminum paste comprises by weight: A. 62-72.5 weight percent of finely divided aluminum flakes;   B. 1.0-3.0 weight percent of stearic acid; and   C. 24.5-37 weight percent of exempt mineral spirits.   
     
     
       17. The process of claim 16 wherein said printing ink comprises by weight approximately: A. 42 percent of said resin binder;   B. 16 percent of said leafing grade aluminum paste; and   C. 42 weight percent of said solvent.